Creating a curved cutter to cut into a sphere - Making a Jack-o-lantern
Okay, I found the answer here: What's the most elegant way to cut shapes out of a mesh. I created a bezier curve that covered the curve where I wanted to put the face cut, then I applied a curve modifier to the jack-o-lantern face mesh and moved it into position. Next I applied the boolean operator on the pumpkin using the face and the difference setting. That neatly cut the face out of the pumpkin, giving me the Jack-o-lantern I wanted. Well, almost. I messed up a couple of things (make sure your face is deep enough to cut far enough into the pumpkin) and have to go back and fix them, but the general purpose works.

I hope someone finds this helpful.